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BMX SERIES III CONSOLE
8.3 PPM METER
The optional Peak Program Meter is a peak level indicating meter which can be supplied to replace or
augment the standard VU meters. The PPM fully conforms to British Standard 4297:1968, which specifies
the characteristics for the meter movement and the overall performance when connected to the required
drive circuitry.
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FIGURE 8.4 PEAK PROGRAM METER
The PPM has a faster rise than standard VU meters, and its dynamic characteristics are radically different.
The rise time is measured with isolated variable length tone bursts of 5 kHz sinusoidal voltage, whose
steady-state value will result in a "0" reference reading. The burst times and scale indications are as follows:
100 ms = 0 dB, 10 ms = -2.5 dB, 5 ms = -4 dB, and 1.5 ms = -9 dB. The fall-back time is defined as between
2.5 and 3.2 seconds for the pointer to fall from +4 to -20 after the removal of a steady-state 1 kHz sinusoidal
voltage.
8.4 REDUNDANT POWER SUPPLY COUPLER UNIT
The Redundant Power Supply Coupler Unit (PR&E #99-76) is used whenever redundant power is desired.
When two power supplies are connected to the unit, the power supply voltages are diode-coupled, with
the highest of the two voltages being supplied to the console. If there is a voltage failure, redundant power
is instantaneously supplied to the console, and the Remote Power Fail Indicator on the coupler unit is
illuminated.
The unit should be installed adjacent to the two console power supplies, and connected with the two
prefabricated cables supplied. The connections to the supplies and to the console are made to the heavy–
duty barrier strips on the rear of the coupler. The cables are color-coded, and the corresponding color names
are printed adjacent to the terminal strips.
NOTE: The high-current diodes used in the coupler have very low forward voltage drop and, therefore,
do not add significantly to the heat dissipation of the power supply system. However, the second power
supply in a redundant system does add approximately 50 watts of heat, due to the excitation current
consumed by the power transformers.
REVISION B
206
PACIFIC RESEARCH & ENGINEERING
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